Method of incinerating refuse

ABSTRACT

A METHOD AND APPARATUS FOR INCINERATING SOLID REFUSE IN WHICH LAREGE AMOUNTS OF USEFUL BY-PRODUCTS ARE RECOVERED AND WHICH IS SUBSTANTIALLY AIR POLLUTION FREE. THE INCINERATOR INCLUDES A FEED-SHAFT, A COMBUSTION CHAMBER INCLUDING A LOW TEMPERATURE, MEDIUM TEMPERATURE AND HIGH TEMPERATURE ZONE HAVING A REDUCING ATMOSPHERE, AND A CHEMICAL REACTION ZONE HAVING AN OXIDIZING ATMOSPHERE. UNSORTED REFUSE ALONG WITH SELECTED ADDITIVES ARE PLACED INTO THE INCINERATOR ON TOP OF A COKE-BED IN THE HIGH TEMPERATURE ZONE. DURING INCINERATION, DISTILLATES FROM LOW TEMPERATURE PYROLYSIS IN THE LOW TEMPERATURE ZONE, AND HIGH TEMPERATURE PYROLYSIS IN THE MEDIUM TEMPERATURE ZONE, ARE WITHDRAWN THROUGH CONDENSERS. A VARI ABLE SPEED FAN OPERABLY EXHAUSTING THE CHEMICAL REACTION ZONE IS OPERATED TO CREATE A NEUTRAL PRESSURE POINT BETWEEN THE MEDIUM TEMPERATURE AND THE HIGH TEMPERATURE ZONE WHEREBY THE PYROLYSIS DISTILLATES MAY BE EASILY SEPARATED FROM A STREAM OF HIGH TEMPERATURE VOLATILES AND CO PRODUCED IN THE HIGH TEMPERATURE ZONE. THE STREAM OF AIR BLOWING ACROSS THE REFUSE CARRIERS THE HIGH TEMPERATURE VOLATILES INTO THE CHEMICAL REACTION ZONE. THE CHEMICAL REACTION ZONE HAS A CHECKER-WALL CONSTRUCTED OF VARIOUS BRICKS SO THAT THE VOLATILES REACT WITH THE BRICKS TO FORM BASIC AND ACIDIC SLAG OXIDES. THE SLAG OXIDES CONDENSE AND FLOW INTO THE HEARTH OF THE HIGH TEMPERATURE ZONE. MOLTEN IRON COLLECTS IN THE INTERSTICES OF THE COKE-BED AND IS REMOVED BY CASTING.

Oct. 10, 1972 ENGLE 3,697,256

METHOD OF INCINERATING REFUSE Filed Feb. 8, 1971 2 Sheets-Sheet 1ADblTu/Es REFUSE CONVEYING MEANS C LOW TEMP. 8 ,3 PYROLYSIS GAS B ZONE NSCRUBBER u 5 AIR 5 g euzcmosrzmc T MEDIUMTEMP. PRECIPITATOR 5 REDUCINGZONE #za'a'T'fm ,3

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Oct. 10, 1972 l. B. ENGLE 3,697,256

METHOD OF INCINERATING REFUSE Filed Feb. 8, 1971 2 Sheets-Sheet 2ADDITWES CONVEYOR GAS SCRUBBER ELECTROSTATIC PRECIPITATOR 40 T ZINVENTOR.

IB.ENELE.

ATTZYS" United States Patent 3,697,256 METHOD OF INCINERATING REFUSEIsaiah B. Engle, Rte. 3, Tiflin, Ohio 44883 Filed Feb. 8, 1971, Ser. No.113,167 Int. Cl. F23g 5/02; C21b /00; C221) 7/00 U.S. CI. 7540 7 ClaimsABSTRACT OF THE DISCLOSURE A method and apparatus for incinerating solidrefuse in which large amounts of useful by-products are recovered andwhich is substantially air pollution free. The incinerator includes afeed-shaft, a combustion chamber including a low temperature, mediumtemperature and high temperature zone having a reducing atmosphere, anda chemical reaction zone having an oxidizing atmosphere. Unsorted refusealong with selected additives are placed into the incinerator on top ofa coke-bed in the high temperature zone. During incineration,distillates from low temperature pyrolysis in the low temperature zone,and high temperature pyrolysis in the medium temperature zone, arewithdrawn through condensers. A variable speed fan operably exhaustingthe chemical reaction zone is operated to create a neutral pressurepoint between the medium temperature and the high temperature zonewhereby the pyrolysis distillates may be easily separated from a streamof high temperature volatiles and CO produced in the high temperaturezone.

The stream of air blowing across the refuse carries the high temperaturevolatiles into the chemical reaction zone. The chemical reaction zonehas a checker-wall constructed of various reactive bricks so that thevolatiles react with the bricks to form basic and acidic slag oxides.The slag oxides condense and flow into the hearth of the hightemperature zone. Molten iron collects in the interstices of thecoke-bed and is removed by casting.

BACKGROUND OF THE INVENTION This invention relates to a method andapparatus for disposing of solid refuse, including both industrial andhousehold waste.

As society becomes more technically advanced, consumption of consumergoods increases. Increased consumer goods consumption and theaccompanying increased production has created disposal problems thatrequire urgent and technically sound solutions. Because of the diversenature of the many manufacturing processes used to produce an everincreasing variety of goods, the variety of composition of the wastematerials from industry and homes is practically limitless.

The disposal of such refuse has generally been accomplished by land-filloperations or incineration methods. With the increasing emphasis on andrecognition of pollution as one of our major problems, the use of theabovementioned methods has come under severe criticism. Landfills areunsightly and unless carefully controlled, attract undesirable rodents;the possibility that such sites contribute to ground water pollution iscurrently being investigated. Available land suitable for land-filloperations is increasingly diflicult to find, especially near denselypopulated urban areas where a large amount of refuse is generated dailyby the inhabitants. Open burning of household and industrial waste canno longer be tolerated; offensive odors, gases and particulate mattercontribute further to air pollution.

Recent attempts at controlled burning of refuse in furnaces have metonly with partial success; usually such processes are economicallyunfeasible. Generally it has been necessary to separate the wastematerial into ferrous and non-ferrous metals, and non-metallics such aspaper, rags and plastics. Such separation procedure is bothtime-consuming and expensive. Additional problems are presented by theattempted incineration of in dustrial and household waste productstogether. The highly variable calorific characteristics of industrialwaste such as oils, paints, and other organic and inorganic wastes, incombination with household garbage, plastics and paper, makes controlledincineration almost impossible.

Generally, prior art methods of refuse incineration have placed aprimary emphasis on mere volume reduction with only incidental recoveryof low calorie waste gas and a fused mass of non-combustible matter,which may be processed further and used as a construction material.

SUMMARY OF THE INVENTION A method and apparatus for incinerating refuseis disclosed which eliminates air pollution and recovers a substantialnumber of by-products from the refuse.

The incinerator has a combustion chamber with a loW temperature, mediumtemperature, and a high temperature zone, and a chemical reaction zoneconnected to the high temperature zone. Referring to FIG. 1, suitableadditions of limestone, coke, coal and iron oxide are made to theunsorted refuse before it is dumped onto a cokebed in the hightemperature zone of the incinerator. Low temperature pyrolysis of lowmelting materials takes place in the low temperature zone and hightemperature pyrolysis takes place in the medium temperature zone.Variable speed fans pull the distillates produced from the pyrolysisinto condensers. Removal of the pyrolysis-produced volatile hydrocarbonsleaves a residue of amorphous carbon, metals and other inorganics in thehigh temperature zone. The inorganic materials and metals such asaluminum, lead, and zinc, having a boiling point less than that of iron,are volatilized by the high temperature produced by the surfacecombustion of the amorphous carbon. Air passes across this refuse in thehigh temperature zone, and carries the stream of high temperaturevolatiles, air, and a large amount of CO into the chemical reactionzone. The chemical reaction zone has a rear checker-wall constructed ofaluminum silicate, alumina, chrome and magnesite bricks. A variablespeed fan located behind the rear checker-Wall removes the hightemperature volatiles, air and CO from the high temperature zone. Thevolatiles react with the bricks of the checker-Wall and are convertedinto slag oxides which condense and flow down the checker-walls into thehearth of the high temperature zone. Molten iron collects in theinterstices of the cokebed. The less dense molten slag is removed andquenched. Iron of good quality is removed from the hearth.

An object of this invention is to provide a pollution-free method forincineration of refuse.

A further object of this invention is to provide an economical methodfor incinerating refuse whereby the refuse may be converted into usefulsolids, liquids and gases.

A still further object of this invention is to provide a method forincinerating refuse whereby a high quality iron is obtained.

The process and apparatus of the present invention will be more easilyunderstood by reference to the appended drawings which are intended toillustrate, but not to limit, the method and apparatus of thisinvention.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings:

FIG. 1 is a flow chart outlining the steps of the method of theinvention;

FIG. 2 is a longitudinal section view of an incinerator plant inaccordance with the invention.

3 DESCRIPTION OF THE PREFERRED EMBODIMENT The incinerator includesconventional means such as a link-belt conveyor 11 for conveying therefuse 12, a feed-shaft 13, a combustion chamber 14 and a chemicalreaction zone 15.

The feed-shaft 13 is constructed of metal such as A: inch steel plate.The diameter of the feed-shaft 13 determines the maximum dimension ofthe refuse 12 which can be charged to the incinerator 10. Preferably theinternal diameter of-the feed-shaft 13 should be limited to about 96inches for maximum combustion efliciency. The feedshaft 13 extends intothe combustion chamber 14 to permit a better seal of the refuse 12packed into the feedshaft 13.

The combustion chamber 14 includesa low temperature zone 16, a mediumtemperature zone 17, and a high temperature zone 18. The low temperaturezone 16 of the combustion chamber 14 can be constructed of any type ofmaterial capable of withstanding temperatures up to about 1800 F. Avariable speed fan 19, pulls volatiles such as water, hydrocarbons andother distillates through louvers 20 into condensers 21.

The medium temperature zone 17 is constructed of fire brick 22 capableof withstanding a maximum operating temperature of about 2500 F.Manometers 23 are connected through the inner walls of the mediumtemperature zone 17, to establish a neutral point, to be explained indetail hereinafter.

The high temperature zone 18 is defined as extending from the fire brick22 to the bottom hearth floor 24. An upper header. 25 and a lower header26 along with cooling pipes 27 are positioned in the wall to water coolthe high temperature zone 18. The cooling pipes 27 are mechanicallysupportedvby thermally stable concrete. The lower. header 26 hastuyeres28. for feeding air into the high temperature zone ,18. It is preferredthat the air be preheated before being fed into the high temperaturecombustion zone 18 in order to obtain maximum temperature in the .hightemperature zone 18. The preheated air is fed from a preheating unit 29through bustle pipes 30, and through the tuyeres 28 into the hightemperature zone 18. A water cooled curtain wall 31 extends downwardly'into the high temperature zone 18. A tap 32 for molten slag and metal ispositioned at the lowermost point in the sloped hearth floor 24. Jets 33for oil or gas are provided to ignite the coke. The curtain-wall 31prevents the coke-bed from shutting off the flow of volatiles into thechemical reaction zone 15. The curtain-wall 31 also increases the gasvelocity into the chemical reaction zone 15.

The chemical reaction zone is connected to the high temperature zone 18.The reaction zone 15 has a roof 34 of silica bricks, sidewalls 35 ofhigh-alumina brick, and a rear checker wall 36 constructed of aluminumsilicate, alumina, chrome and magnesite bricks. The bracks in thechemical reaction zone 15 are laid up with a neutral chrome cement. Thefloor 37 of the reaction zone 15 is constructed of magnesite bricks, andis sloped and troughed in the direction of the high temperature zone 18in such a manner that the slag flows onto the hearth floor 24. A door Bmay be built into the wall 35 to allow access to zone 15 for the purposeof renewing the floor 37 with crushed limestone. The oil or gas burnerand air inlets 33 placed in the outer periphery of the high temperaturezone walls are used to ignite the coke. After the chemical reaction zone15 is heated to operating temperature, the combination oil or gasburners and air inlets 33 are shut off. Air may be supplied through theinlets 33 during incineration operation. Since it is not necessary. touse preheated air in the chemical reaction zone 15, anair supply sourcemay be provided separate from thepreheater unit 29 to lessen the demandon the preheater unit 299A variable speed fan 39, whose use will beexplained in detail hereinafter, pulls gases from the high temperaturezone 18 through an electrostatic.

precipitator 40 and a gas scrubber 41, before discharging the gases intothe atmosphere.

Referring to FIG. 2, a charge of coke 42 suflicient to fill the hightemperature zone 18 is placed into the incinerator 10. Combination gasburners and air inlets 33 in the chemical reaction zone 15 are used toheat the chemical reaction zone 15 only in the start-up of theincinerator. Conventional package spreading devices should be used toopen or spread the refuse on the conveyor 11. The refuse 12 to betreated, consisting of unsorted household and industrial Waste products,dewatered sewage and agricultural products, is introduced continuouslyinto the incinerator 10 by the conveyor 11. The refuse 12 is monitoredby a first operator, who works in conjunction with a second operatormonitoring the molten slag 43 and molten metal 44, withdrawn at the slagor metal tap 32. Obviously the composition of refuse- 12 to be dis posedof will vary greatly. A single load of refuse 12 may contain glass andplastic containers, waste food, paper products, metals such as steel,copper, aluminum, titanium, and large objects such as television sets,chairs and scrap lumber. The operator responsible for monitoring therefuse 12 before it is dumped into the feed-shaft 13 must decide, on thebasis of visual observation, and in conjunction with the slag and metalanalyses, whether to add limestone and iron oxide along with the cokeand coal which are added continuously. For example, if a large amount ofaluminum cans or foil are present, the operator will want to add ironoxide, as iron ore or mill scale, to the refuse 12. The coke and coalare used to maintain the furnace operating temperatures, and the coalfunctions further to prevent the glass waste products from weldingtogether and blanketing the charge. The limestone functions as a flux toreduce the fusion point of the slag produced. The additions oflimestone, coke, high-coking coal or iron ore are manually controlled bythe first opera-v tor from his visual analyses of the raw refuse 12being conveyed past his station.

Burning of the coke-bed 42 produces an operating temperature in the hightemperature zone 18 of about 3600 F.; the use of air preheated to about1000 F. or higher, produces an operating temperature of about 4000 F. Atemperature gradient of about 25 00 F. in the medium temperature zone 17and of about 1800 F. in the low temperature zone 16 is maintained duringthe operation of the incinerator.

As the refuse 12 enters the feed-shaft 13 during the start-up of theincinerator 10, it falls onto the preheated coke-bed 42. As pyrolysis ofthe carbonaceous materials progresses, the residue of the refuse 12,consisting of amorphous carbon, metals and inorganics, having thevolatile hydrocarbons and moisture removed by pyrolysis, is fed bygravity into the high temperature zone 18 and melted. The high operatingtemperature of the cokebed 42 accelerates pyrolysis in the lowtemperature zone 16 and medium temperature zone 17. The variable speedfan 19' pulls the pyrolysis products such as water and hydrocarbonsthrough the louvers 20 and into the condensers 21. Non-condensible gasesare pulled by the fan through the condenser 21 into a gas stripper. Thegas stripper uses conventional methods .to remove entrained tar andvolatiles from the gaseous fraction. The gaseous fraction, containing HS, NH C N and S0 is reacted with H 50 to remove the ammonia derivativesas (NH SO Further treatment of the gaseous fraction with caustic sodasolution will remove H 5, C N 'and S0 The condensing apparatus willyield water, tar, oils and liquor. Further processing of the distillateoils and tars will yield compounds such as olefins, aromatics, paraffinsand napthenes. Processing of the light oil fraction will yield suchcompounds as benzene and toluene- The remaining liquor will contain amajor portion of water,

with minor amounts of acids, ketones and aldehydes. Catalytic crackingapparatus may be connected prior to the condensers 21 to reduce theamount of tar formation and increase the higher boiling fraction of oilsrecovered. The additions of high-coking coal made to the refuse 12 helpsto upgrade the calorific value of the gas recovered.

Removal of moisture and hydrocarbon distillates in the low temperaturezone 16 solves a problem that has confronted prior art methods ofincineration. Removal of moisture and other low-temperature distillatesby use of a primary or separate drying chamber is not economicallyfeasible. Unless the distillates and moisture produced by pyrolysis arewithdrawn prior to the operation of the high temperature zone 18 andchemical reaction zone 15, the incineration process is severelyinhibited.

Prior art incineration methods have also encountered difficulties inpreventing escape of loose paper and ash. Paper products char easily,and the movement of air and gas in such incinerators has interfered withthe operation of electrostatic precipitators and gas scrubbers byoverloading them with ash and other particulate matter. As the cokeburns in the high temperature zone 18, the paper and other refuse 12such as bottles and cans, tend to agglomerate. Formation of thisagglomerate prevents the ash from flying around the incinerator 10 andinterfering with the operation of the electrostatic precipitators 40 andgas scrubber 41. The coke prevents the refuse from the welding together,and acts somewhat as a filter to minimize the movement of ash andparticulate matter into the chemical reaction zone 15.

It is crucial that the tuyeres 28 which carry the preheated air into thehigh temperature zone 18 be positioned in such a manner that theairblast is fed across the refuse 12. By adjusting the variable speed fans19 and 39 such that a neutral pressure point is obtained between themedium and high temperature zones, the products of combustion obtainedfrom the high temperature zone 18 are carried by the variable speed fan39 into the chemical reaction zone 15 and through the checker walls 36.The use of the neutral pressure point? to separate the combustionproducts, i.e., the products produced by the pyrolysis of carbonaceousproducts, from the CO, metal and inorganic volatiles produced by hightemperature combustion, may be supplemented by gas analyses. The Ncontent of the pyrolysis-produced gases and distillates should be keptto a minimum. The CO is converted into CO in the chemical reaction zoneby the oxidizing atmosphere.

The refuse 12 in the high temperature zone 18 will consist in largeparts of metals such as copper, iron, titanium and glass products. Thelower melting metals will be volatilized along with, for example, thesodium and potassium ions of the glass products. The air blast acrossthe refuse 12 produces a turbulent flow of a gaseous mixture of hot air,CO gas from the combustion of amorphous carbon present, and volatiles.Such turbulence enables the volatiles to react more fully with the hightemperature surface of the brickwork in the chemical reaction zone 15-The variable speed fan 39, carries the gaseous mixture through thechecker wall 36 and through an electrostatic precipitator 40 and gasscrubber 41.

The rear checker walls 36, constructed of basic, neutral and acidbricks, willreact with the hot volatiles to form reaction products ofvarious oxides. The reaction products form the slag 43 which condensesand flows down the inclined floor 37 of the reaction zone 15 and ontothe hearth 24 of the high temperature zone 18. The molten slag may bewithdrawn through the molten slag taps 32 as desired. It is convenientto quench the slag to produce a fine particulate substance. A largeamount of trace elements have been found to be present making the slaguseful as a fertilizer additive. Other uses include processing the slagfor material suitable for road-Work or building material, or the slagmay be used as material for clean land-fill operations.

Molten iron accumulates in the interstices of the cokebed 42 and may bewithdrawn through the metal tap 32. Removal of the more volatileelements from the molten iron will facilitate the production of a highquality iron, low in phosphorous and sulfur.

What I claim is:

1. A method of incinerating household and industrial refuse in anincinerator having a vertically extending combustion chamber with anupper low temperature zone, an intermediate medium temperature zone anda lowermost high temperature zone interconnected by a common verticalpassage through which refuse may pass which passage has its upper endexposed to receive refuse and its lower end terminated above a floor insaid high temperature zone and a chemical reaction chamber extendinglaterally from one side of said lowermost high temperature zone, saidlow temperature zone having first exhaust means operably connectedthereto, said chemical reaction zone having second exhaust meansoperably connected thereto, said method comprising the steps of (a)igniting a coke bed in said high temperaturezone,

(b) adding coke and coal to the refuse prior to its entry into saidcombustion chamber,

(c) filling said combustion chamber with said admixed refuse,

(d) directing a lateral flow of preheated air across the hightemperature zone and (e) adjusting the said first and second exhaustmeans to create a neutral pressure point between said high and mediumtemperature zones whereby high temperature pyrolysis products from themedium temperature zone and low temperature pyrolysis products from thelow temperature zone are removed by the said first exhaust means, andhigh temperature volatiles from the high temperature zone are carriedinto said chemical reaction zone, and

(f) removing molten iron from said high temperature zone.

2. The method of claim 1 which further includes the step of addingselected amounts of limestone and iron oxide with said coke and coal tothe refuse prior to its entry into said combustion chamber.

3. The method of claim 2 wherein the amounts of limestone and iron oxideadded to said refuse are continuously adjusted by an operator inproportion to the composition of the refuse being incinerated.

4. The method of claim 1 which further includes the step of directingthe flow of high temperature volatiles within said chemical reactionchamber through a wall of checker brick of varied composition, saidchecker wall including bricks of acid, neutral and basic composition, toselectively condense said volatiles into slag oxides.

5. The method of claim 4 wherein said checker brick wall comprisesaluminum silicate, alumina, chrome and magnesite bricks.

6. The method of claim 1 which further includes the steps of directingthe flow of said pyrolysis products from said low and medium temperaturezones through at least one condenser to convert a portion thereof intoliquid condensate.

7. The method of claim 1 which further includes the step of directingair through a preheating unit and thence into said high temperaturezone.

References Cited UNITED STATES PATENTS 3,554,143 1/1971 Rodgers et al-15 X 3,511,194 5/1970 Stookey 110-8 R 485,392 11/ 1892 Koneman 75-431,755,845 4/1930 Snyder 75-41 X 2,029,576 2/1936 Kolb 110-15 HENRY W.TARRING, Primary Examiner US. Cl. X.R.

